1. Field of the Invention
The invention relates to a pinion gear carriage in a planetary gear mechanism for use in an automatic transmission, and in particular to the frame, bearing and washer structures for a pinion gear carriage in which no separate lubricating device is employed.
2. Description of the Prior Art
A planetary gear mechanism, such as is commonly used in automatic transmissions, comprises a sun gear, at least one planet gear, and a plurality of pinion gears for transmitting rotation from the sun gear to the planet gear. The pinion gears are rotatably supported within a carriage which rotates with the sun gear.
The pinion gear carriage includes a plurality of fixed, radially-symmetrically-arranged shafts, one for each pinion gear running between two opposing member of the carriage. Each shaft is provided with a bearing, such as a needle bearing to ease rotation of the pinion gears about the shafts. In addition, thrust washers are installed on either side of the pinion gears between the gears and the walls of the carriage to prevent frictional contact therebetween. Normally, two or more washers are used on each side so as to limit the gradient of rotational speed across each washer.
The frame of the carriage itself usually consists of a pair of parallel, concentric, annular disks welded together or formed integrally. Within the space between the disks, the sun gear will engage the innermost teeth of the pinion gears. In addition, the carriage frame includes a means for engaging with a central shaft which rotates coaxially with the sun gear. The central shaft and the sun gear are connected via a differential mechanism so as to rotate together, but at different speeds. Thus, as the sun gear rotates, the pinion gears will rotate at a rate proportional to the difference in speed between the sun gear and the central shaft, and transmit this rotation to the planet gears.
It is necessary to provide lubrication for the needle bearings of the pinion gears. Prior art carriages have employed separate lubrication devices for each bearing. This design necessarily increases the cost of manufacture and adds a plurality of elements of imperfect reliability. Considering the difficulty and therefore cost of automatic transmission repair, any increase in reliability will significantly improve user convenience.